1. Technical Field
The present invention relates generally to crash sensing systems for automotive vehicles, and more particularly, to a backup power supply for a crash notification system and to a method of operating the same.
2. Background
Accident sensing systems typically use accelerometers to determine which safety devices to deploy. For example, a front accelerometer determines the deceleration of the vehicle. The restraints module deploys the front airbag in response to the deceleration being severe or above a predetermined amount. The deceleration corresponds to a crash impact on the front of the vehicle. Side airbag sensors operate in a similar manner in that a laterally mounted acceleration sensor measures the side deceleration on the vehicle due to a crash.
Telematics systems are currently offered by various automakers. Such systems typically contact a response center in response to the deployment of the airbags. The response center then notifies the police that some type of accident has occurred. Such a system, however, does not provide an indication to the severity of the crash.
Some telematics systems incorporate a backup battery to power the system in the event that the main battery or the vehicle wiring is damaged. During maintenance of the vehicle, however, the backup battery may be activated causing unnecessary drain on the battery. This is important especially when an extended life one-time use battery is used in the system. Such batteries are desirable to be used in such applications.
Therefore, it would be desirable to provide a crash notification system that provides a circuit to prevent unnecessary usage of the backup battery.
The present invention provides a crash notification system that uses a backup battery when a number of conditions are met to prevent the unnecessary use of the backup battery.
In one aspect of the invention, a crash notification system interfacing coupled to a communication network includes a main battery having a main battery voltage, a backup battery having a backup battery voltage, a restraint control module generating an emergency notification signal, and a telematics control unit coupled to the main battery, the backup battery and the restraint control module. The telematics control unit operates from the backup battery in response to the main battery voltage and the emergency notification signal.
In a further aspect of the invention, a method of operating a crash notification system having a main battery, a backup battery, a restraint control module, and a telematics control unit comprises sensing a main battery voltage, generating an emergency notification signal at the restraint control module and having a first state indicative of an undeployed restraint device and a second state indicative of an event threshold such as that of a deployed restraint device, when an emergency notification signal is in a second state and the main battery voltage is below a predetermined level, operating the telematics with the backup battery.
One advantage of the invention is that unnecessary use of the backup battery is prevented. This allows the design of the backup battery system to be less costly.